Conventionally, there is a known side bodyshell with a so-called floating frame structure, in which horizontal frames are joined to an outside plate, and over the horizontal frames, vertical frames are provided across the horizontal frames. For example, Patent Literature 1 discloses a side bodyshell of a railcar, in which: an outside plate includes a window opening and an entrance opening, which are arranged alternately in the railcar longitudinal direction; two types of horizontal frames having different heights from each other (the term height means a protruding dimension of each horizontal frame protruding inward in the railcar width direction from the outside plate) are joined to the outside plate.
Specifically, the side bodyshell disclosed in Patent Literature 1 includes a pair of first horizontal frames having a great height. One of the first horizontal frames is disposed immediately above the window opening of the outside plate, and the other first horizontal frame is disposed immediately below the window opening. Second horizontal frames having a small height are arranged between these first horizontal frames (i.e., on a pier panel between the window opening and the entrance opening), and also arranged above and below the first horizontal frames. Vertical frames are provided in a manner to cross these horizontal frames. Such a vertical frame is divided up at positions corresponding to the pair of first horizontal frames into an upper vertical frame portion, a middle vertical frame portion, and a lower vertical frame portion. These vertical frame portions are connected to each other via coupling members.
Each vertical frame portion has a hat-shaped cross section and includes flanges. The flanges of each vertical frame portion are joined to second horizontal frames. The coupling members, which connect the vertical frame portions together, extend in the railcar longitudinal direction along the first horizontal frames, such that each coupling member covers a gap between vertical frame portions from inside in the railcar width direction. Both ends of the coupling members are joined to the first horizontal frames.
Patent Literature 2 discloses a bodyshell frame structure of a railcar, in which horizontal frames are arranged in priority to vertical frames, and the vertical frames are brought into contact with and welded to the horizontal frames. According to Patent Literature 2, owing to such a structure, the horizontal frames can be provided continuously in the railcar longitudinal direction without causing the horizontal frames to be divided up by the vertical frames, and the number of horizontal frames can be minimized since the horizontal frames need not be divided up.